There is currently a strong trend toward downsizing existing structures and fabricating smaller structures. This process is commonly referred to as microfabrication. One area in which microfabrication has had a sizeable impact is in the microelectronic area. In particular, the downsizing of microelectronic structures has generally allowed the structures to be less expensive, have higher performance, exhibit reduced power consumption and contain more components for a given dimension. Although microfabrication has been widely active in the electronics industry, it has been applied to other applications such as biotechnology, optics, mechanical systems, sensing devices, and reactors.
One method employed in the microfabrication process is imprint lithography. Imprint lithography is typically utilized to transfer the original features of a stamp or mold onto softer materials. The imprinted materials may be used either as the final structures or etch masks to pattern underlying thin films. The thin films patterned can be dielectrics, semiconductors, metals or organics. Implementation of this method encompasses an initial step of making an imprint mold or stamp. To make such devices as diodes and transistors using imprint lithography, a single stamp may be required to contain all the pre-aligned information for the subsequent processing steps, and thus, needs to be three dimensional in shape.
Silicon microprocessing technologies, which include photolithography and plasma etching, are often used for fabricating stamps for imprint lithography. With the conventional methodologies of microprocessing, a minimum feature in the sub-micron or nano-meter scales can be defined in a reliable and repeatable manner. However, achieving complex 3-dimensional (3D) structures with multiple levels is limited as non-planarity of the surface increases.
There are two reasons for the limitation. First, focusing capability of the photolithographic optics is lost as the relative height of one surface from another exceeds its depth of focus (DOF). Second, it becomes increasingly difficult to obtain a thin uniform film of photoresist of spin coating once higher aspect ratio features are present. These attributes are more pronounced where feature size is smaller and the overall geometry is more complex. As a result, the conventional approaches are limited in achieving complex 3D features with a high aspect ratio and multiple levels.
Accordingly, what is needed is a method and system that addresses the above-delineated problems associated with the fabrication of microprocess equipment. The method and system should be simple, cost effective and capable of being easily adapted to existing technology. The present invention addresses this need.